This invention relates generally to slide fasteners and in particular to an automatically locking slider for slide fasteners. Still more specifically, the invention is directed to an automatic slider lock mechanism of the type including a leaf spring overlying the slider body and having a locking pawl at one end which normally projects into the Y-shaped guide channel in the slider body to lock the slider against movement on a pair of fastener stringers and which retracts away therefrom to unlock the slider when a pull is exerted on the pull tab of the slider.
In the known automatic slider lock mechanism of the above described type, the locking leaf spring arranged longitudinally over the top wing of the slider body is usually provided with a curved portion at its front end, which portion is the principal part lending the desired resiliency to the spring, and with a locking pawl at its rear end which normally projects into the slider body for interference contact with the rows of interlocking fastener elements passing therethrough. The pull tab of the slider is pivotally connected to the locking leaf spring at a point intermediate both ends thereof, in such a manner that the locking pawl retracts from within the slider body upon exertion of a pull on the pull tab.
The automatic slider lock mechanism of this prior art configuration manifests a serious deficiency when, for instance, a garment or like article to which there has been attached the slide fastener incorporating the slider in question is subjected to ironing operation. The pressure exerted upon the slider from above is easy to permanently strain the curved portion of the locking leaf spring, thereby causing a change in its spring constant and hence seriously impairing the performance of the lock mechanism.
In an attempt to overcome this deficiency, it has been proposed to provide a projection or projections upon the top wing of the slider body for protection of the curved portion of the locking leaf spring from pressures applied from above the slider. The slider body having such protection means, however, is usually produced by die casting, and die-cast sliders are of course significantly more expensive than those produced by pressing operation.